There have been conventionally known collaborative filtering methods as a technique that identifies an item that is more likely to attract the interest of a user who is searching for an item on Web pages or in a database and presents the identified item as a recommended item. One of the collaborative filtering methods identifies a similar user based on the information on the user and the item that the user has accessed, and presents the item that has been accessed by the similar user as a recommended item. Another one of the collaborative filtering methods identifies an item similar to the item that the user has accessed based on the similarity between items, and presents the similar item as a recommended item.
Japanese Patent Application Publication Nos. 2006-48320, 2011-135183, and 2012-22365 disclose techniques that recommend information relevant to the contents that the user is browsing.